3 years ago

Covalently Bonded Perylene–DiiodoBodipy Dyads for Thiol-Activatable Triplet–Triplet Annihilation Upconversion

Covalently Bonded Perylene–DiiodoBodipy Dyads for Thiol-Activatable Triplet–Triplet Annihilation Upconversion
Evan G. Moore, Kejing Xu, Jianzhang Zhao
To achieve activatable triplet–triplet annihilation (TTA) upconversion, we linked a diiodoBodipy triplet photosensitizing unit and perylene triplet energy acceptor/annihilation/emitter using a disulfide bond (dyad BP-1), which can be selectively cleaved by thiols. For comparison, a reference dyad featuring a shorter and more chemically robust 1,2,3-triazole linker between the two components was also prepared (dyad BP-2). The photophysical properties of these compounds have been studied using steady-state and time-resolved transient spectroscopies; forward singlet energy transfer and backward triplet energy transfer (ping-pong energy transfer) were observed. For BP-1, the rate for forward intramolecular Förster resonance energy transfer from perylene to diiodoBodipy is kFRET = 1.9 × 108 s–1, while the backward triplet–triplet energy-transfer (TTET) process from diiodoBodipy to perylene was slightly slower, with kTTET = 3.7 × 107 s–1. For BP-2, faster energy-transfer kinetics were determined (kFRET = 3.1 × 108 s–1 and kTTET = 8.4 × 107 s–1, respectively). Interestingly, we found the FRET rate constant is more critically dependent on the length of the linker than the corresponding TTET process, which may have important implications for the design of supramolecular TTA architectures. Lastly, upon cleavage of the disulfide bond in BP-1, intramolecular FRET was effectively shut down, and instead intermolecular TTET was observed, allowing for thiol-activatable TTA upconversion with an improvement in upconversion quantum yield from 0.03% to 0.5% in the presence of thiols.

Publisher URL: http://dx.doi.org/10.1021/acs.jpcc.7b06922

DOI: 10.1021/acs.jpcc.7b06922

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